The present invention relates generally to monitoring the cleansing of waste liquid, such as oily waste water.
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
Presently, liquid wastes are collected and stored on board ships during transit or while moored in restricted waters for cleansing treatment by membrane separation systems before subsequent waste disposal discharge within a limited period of time, such as 6 hours. Costly waste oil content monitoring systems are currently utilized to check performance of the water cleansing membranes by measuring the concentration of oil in the permeate to be discharged overboard. With respect to low concentrations of oil emulsified in the discharges, such measurements of oil content are not reliable because of various types of contaminants in the permeate, such as air bubbles and solid particles which adversely affect sensor detection involved to obtain the measurements. It is therefore an important object of the present invention to provide for monitoring of the cleansed waste water in such a manner as to more reliably check membrane performance in its oil separation cleansing action.
In accordance with the present invention, the measurement of low oil content concentrations in oily waste water discharges is avoided in favor of detecting optical properties of atmospheric air to which the surface of oily waste liquid is exposed during flow along a predetermined path through an enclosure within which the air is confined with a certain amount of light energy therein for optical detection of variation in light by a sensor. Thus, the signal data from the sensor will reflect variation in absorption of light by the waste liquid at a surface thereon during said flow, which is affected by the presence of any waste oil film on the waste liquid being monitored. Such signal data may therefore be utilized to more reliably indicate membrane performance integrity.